1. Field of the Invention
The present invention relates to a bearing assembly with a rotation detection device that can be used for the detection of rotations occurring in various machines and equipments, for example, the detection of rotation for the purpose of controlling a compact motor, for the detection of rotation for the purpose of position detection in a business machine or equipment or for the detection of a joint angle of an articulated robot.
2. Description of the Prior Art
For detecting a rotation or an angle of, for example, a joint of an articulated robot, a bearing assembly with a rotation detection device of a kind having a rotation detecting device integrated in a bearing assembly for supporting a shaft at an articulation is employed. Such a bearing assembly with a rotation detection device is desired to be compact in size, and this is particularly true where the bearing assembly is intended for use in a knuckle joint of a robot. In order to meet with this desire, the applicant of the present invention has suggested such a bearing assembly with a rotation detection device as shown in FIG. 22, which is disclosed in the Japanese Laid-open Patent Publication No. 2004-37133 published Feb. 5, 2004.
The bearing assembly with a rotation detection device shown in FIG. 22 is of a structure including a magnetic generating element 32 arranged on an inner race 51 side, which is a rotating ring, and having a directionality about a rotation axis of such inner race 51 (magnetic variation in a circumferential direction), and a magnetic line sensor 33 arranged on an outer race 52 side, which is a stationary ring, in opposition to the magnetic generating element 32. The magnetic line sensor 33 is operable to detect a magnetism emanating from the magnetic generating element 32, which is made up of a permanent magnet 32A and magnetic yokes 32B and is fitted to the inner race 51 through a magnetic generating element fitting member 45 that is press-fitted onto an outer diametric surface of the inner race 51. Since the inner race 51 rotates together with a rotary shaft 40, the magnetic generating element 32 also rotates together with the rotary shaft 40 through the magnetic generating element fitting member 45. The magnetic line sensor 33 referred to above is fitted to the outer race 52 through a sensor fitting member 57 that is press-fitted inside an inner diametric surface of the outer race 52.
It has, however, been found that in the bearing assembly with a rotation detection device of the structure discussed above, the manner of incorporating the rotation detecting device into the bearing assembly is not optimized and has a substantial length in a direction axially thereof. In other words, since the magnetic generating element 32 is fitted to the inner race 51 through the intervention of the magnetic generating element fitting member 45 that is press-fitted onto the outer diametric surface of the inner race 51, the axial dimension of the entire assembly tends to be substantial and downsizing thereof is not sufficient.